An adjustable rail brace assembly for buttressing the head of a rail includes a rail brace having surfaces for engaging the head and the base of the rail and a vertically extending wedging face, a cover plate for retaining the brace having a vertical wedging face which compliments the brace wedging face, and an interlock for interlocking the brace wedging face and the cover plate wedging face such that the brace and the cover plate can move relative to each other in a vertical plane, but are restrained from moving relative to each other in a horizontal plane, and an elastic fastener for engaging the cover plate to prevent vertical movement of the cover plate.